There has been increasing interest in a range of problems which Kit Fine has felicitiously called (in unpublished work) modal1 slippery slope paradoxes. A good, succinct example of this type has recently been described by Nathan Salmon in his paper, 'Impossible Worlds' (Analysis 44.3, June 1984, pp. 114-172).

My purpose here is to point out that this example, like some of the others, is paralleled by what might be called a temporal slippery slope paradox, as can be seen by considering the following principle (which parallels Salmon's principle (2')):

(T) If a given artefact x is assembled from a set of components y, then x could be completely disassembled and later re-assembled from another set of components z which sufficiently overlaps y; but x could not later be re-assembled from any set of components z' which does not sufficiently overlap y.

This principle is as intuitively appealing as many of those under lying modal3 slippery slope paradoxes, and to see in detail how we might implicitly appeal to it, suppose that we take our watch x to a watch-maker who completely disassembles it. …

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Notice that the above case is not identical with that of the famous ship of Theseus4, which is continuously modified over a long period without being completely dismantled….